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ABSTRACT: We examine the quantum spin state of a single nitrogen-vacancy (NV) center in diamond at room temperature as it makes a transition from the orbital ground state (GS) to the orbital excited state (ES) during nonresonant optical excitation. While the fluorescence readout of NV-center spins relies on conservation of the longitudinal spin projection during optical excitation, the question of quantum phase preservation has not been examined. Using Ramsey measurements and quantum process tomography of the optical excitation process, we measure a trace fidelity of F=0.87±0.03, which includes ES spin dephasing during measurement. Extrapolation to the moment of optical excitation yields F≈0.95. This result provides insight into the interaction between spin coherence and nonresonant optical absorption through a vibronic sideband.
Physical Review Letters 04/2012; 108(15):157602. · 7.37 Impact Factor
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ABSTRACT: We examine the quantum spin state of a single nitrogen-vacancy (NV) center in
diamond at room temperature as it makes a transition from the orbital
ground-state (GS) to the orbital excited-state (ES) during non-resonant optical
excitation. While the fluorescence read-out of NV-center spins relies on
conservation of the longitudinal spin projection during optical excitation, the
question of quantum phase preservation has not been examined. Using Ramsey
measurements and quantum process tomography, we establish limits on NV center
spin decoherence induced during optical excitation. Treating the optical
excitation and ES spin precession as a quantum process, we measure a process
fidelity of F=0.87\pm0.03, which includes ES spin dephasing during measurement.
Extrapolation to the moment of optical excitation yields F\approx0.95. This
result demonstrates that ES spin interactions may be used as a resource for
quantum control because the quantum spin state can survive incoherent orbital
transitions.
11/2011;
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Nature Physics 10/2011; · 18.97 Impact Factor
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ABSTRACT: The exceptional spin coherence of nitrogen-vacancy centers in diamond motivates their function in emerging quantum technologies. Traditionally, the spin state of individual centers is measured optically and destructively. We demonstrate dispersive, single-spin coupling to light for both nondestructive spin measurement, through the Faraday effect, and coherent spin manipulation, through the optical Stark effect. These interactions can enable the coherent exchange of quantum information between single nitrogen-vacancy spins and light, facilitating coherent measurement, control, and entanglement that is scalable over large distances.
Science 11/2010; 330(6008):1212-5. · 31.20 Impact Factor
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ABSTRACT: We demonstrate methods to locally control the spin rotation of moving electrons in a GaAs channel. The Larmor frequency of optically injected spins is modulated when the spins are dragged through a region of spin-polarized nuclei created at a MnAs/GaAs interface. The effective field created by the nuclei is controlled either optically or electrically using the ferromagnetic proximity polarization effect. Spin rotation is also tuned by controlling the carrier traverse time through the polarized region. We demonstrate coherent spin rotations of 5π rad during transport.
Physical Review Letters 09/2010; 105(13):137206. · 7.37 Impact Factor
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ABSTRACT: The localized spin triplet ground state of a nitrogen vacancy (NV) center in diamond can be used in atomic-scale detection of local magnetic fields. Here we present a technique using these defects in diamond to image fields around magnetic structures. We extract the local magnetic field vector by probing resonant transitions of the four fixed tetrahedral NV orientations. In combination with confocal microscopy techniques, we construct a 2-dimensional image of the local magnetic field vectors. Measurements are done in external fields less than 50 G and under ambient conditions. Comment: 9 pages, 3 figures
12/2009;
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ABSTRACT: Two-level systems are at the core of numerous real-world technologies such as magnetic resonance imaging and atomic clocks. Coherent control of the state is achieved with an oscillating field that drives dynamics at a rate determined by its amplitude. As the strength of the field is increased, a different regime emerges where linear scaling of the manipulation rate breaks down and complex dynamics are expected. By calibrating the spin rotation with an adiabatic passage, we have measured the room-temperature "strong-driving" dynamics of a single nitrogen vacancy center in diamond. With an adiabatic passage to calibrate the spin rotation, we observed dynamics on sub-nanosecond time scales. Contrary to conventional thinking, this breakdown of the rotating wave approximation provides opportunities for time-optimal quantum control of a single spin.
Science 11/2009; 326(5959):1520-2. · 31.20 Impact Factor
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ABSTRACT: We report time-dependent photocurrent and transport measurements of sub-bandgap photoexcited carriers in nitrogen-rich (type Ib), single-crystal diamond. Transient carrier dynamics are characteristic of trapping conduction with long charge storage lifetimes of ~3 hours. By measuring the photoexcited Hall effect we confirm that the charge carriers are electrons and by varying the excitation energy we observe a strong turn-on in the photoconduction at ~1.9 eV. These findings shed new light on sub-bandgap states in nitrogen doped single-crystal diamond.
03/2009;
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ABSTRACT: We use single-spin resonant spectroscopy to study the spin structure in the orbital excited state of a diamond nitrogen-vacancy (N-V) center at room temperature. The data show that the excited-state spin levels have a zero-field splitting that is approximately half of the value of the ground state levels, a g factor similar to the ground state value, and a hyperfine splitting approximately 20x larger than in the ground state. In addition, the width of the resonances reflects the electronic lifetime in the excited state. We also show that the spin level splitting can significantly differ between N-V centers, likely due to the effects of local strain, which provides a pathway to control over the spin Hamiltonian and may be useful for quantum-information processing.
Physical Review Letters 10/2008; 101(11):117601. · 7.37 Impact Factor
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C. D. Weis,
A. Schuh,
A. Batra,
A. Persaud,
I. W. Rangelow,
J. Bokor,
C. C. Lo,
S Cabrini,
E. Sideras-Haddad, G. D. Fuchs,
R. Hanson,
D. D. Awschalom,
T. Schenkel
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ABSTRACT: The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in single atoms, such as proposed quantum computers. We describe a single atom injector, in which the imaging and alignment capabilities of a scanning force microscope (SFM) are integrated with ion beams from a series of ion sources and with sensitive detection of current transients induced by incident ions. Ion beams are collimated by a small hole in the SFM tip and current changes induced by single ion impacts in transistor channels enable reliable detection of single ion hits. We discuss resolution limiting factors in ion placement and processing and paths to single atom (and color center) array formation for systematic testing of quantum computer architectures in silicon and diamond.
06/2008;
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Nature Physics.
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ABSTRACT: A quantum memory, composed of a long-lived qubit coupled to each processing qubit, is important to building a scalable platform for quantum information science. These two qubits should be connected by a fast and high-fidelity operation to store and retrieve coherent quantum states. Here, we demonstrate a room-temperature quantum memory based on the spin of the nitrogen nucleus intrinsic to each nitrogen-vacancy (NV) centre in diamond. We perform coherent storage of a single NV centre electronic spin in a single nitrogen nuclear spin using Landau-Zener transitions across a hyperfine-mediated avoided level crossing. By working outside the asymptotic regime, we demonstrate coherent state transfer in as little as 120 ns with total storage fidelity of 88 +/- 6%. This work demonstrates the use of a quantum memory that is compatible with scaling as the nitrogen nucleus is deterministically present in each NV centre defect.
Nature Physics. 7(10):789-793.
